Third, fourth, fifth or even tenth class would be more accurate.
Under the dhimmitude system, Christians (and Jews, if any) are not citizens at asll but treated as enemy aliens.
They cannot have civil service jobs, cannot attend college, cannot get passports or even telephones, cannot have their own newspapers, cannot testify against Moslems, etc. etc. They are not allowed to leave the country for religious pilgrimages, they'd better not complain about their situation to foreigners including their co-religionists in civilized countries, and worship services and teachings are monitors and censored by the Moslem government (in Saudi Arabia, for one, the Christian schools that are allowed are required to use government-published textbooks that denounce Christianity as a false religion.
Their church buildings are limited in size - in Israel those church buildings that existed under the Ottomans or the Jordanians are kept low (inside they have immediate steps into a sort of crater, the only way to get enough space for a raised pulpit and choir loft without a high roof) and unadorned; frequently mosques - even unnecessary and ill-attended ones - are built up against the walls of churches, often on more than one side, to make sure that the church never expands its building (in Egypt it seems to take forever for the Coptic Christians to get govt permission to build a new church - and the moment they finally get permission to build at a particular address a mosque suddenly is thrown up at that spot).
In the Moslem countries it is a serious crime on par with treason, usually a capital offense, to try to proselytize a Moslem - even the relative or spouse of a Christian - to become Christian ... and a capital offense for a Moslem to convert to Christianity.
Hindus, Buddhists and some others that Moslems regard as idol worshippers have it even worse.